以下在MySQL5.0版本适用，其他版本没有验证。
当在SQL中比较字符串和整数的时候，会将两方都转换为float进行比较，会产生意想不到的结果:
mysql> select 'CBA123' = 0;
+-----------------------+
| 'CBA123' = 0 |
+-----------------------+
| 1 |
+-----------------------+
1 row in set, 1 warning (0.00 sec)
等号两边都被转换成0.0
mysql> select 'CBA123' = '0';
+-------------------------+
| 'CBA123' = '0' |
+-------------------------+
| 0 |
+-------------------------+
1 row in set (0.00 sec)
字符串之间的比较不需要类型转换
mysql> select '123CBA' = 123;
+----------------+
| '123CBA' = 123 |
+----------------+
| 1 |
+----------------+
1 row in set, 1 warning (0.00 sec)
字符串 ‘123CBA’被转换成123.0 看一下警告信息:
mysql> show warnings;
+---------+------+--------------------------------------------+
| Level | Code | Message |
+---------+------+--------------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: '123CBA' |
+---------+------+--------------------------------------------+
1 row in set (0.00 sec)
所以在以字符串类型列为筛选条件的时候，还是不要和整数进行比较了。